Field of the Invention
This invention relates to a technical field of semi-conductors, and specifically to a method for preparing graphene, a thin-film transistor, an array substrate, and a display panel.
Description of the Related Art
Extensive studies on graphene have broken out since single-layer graphene was successfully obtained by a UK physicist, Andre Geim, using a mechanical exfoliation method in 2004. Single-layer graphene is a single-layer hexagonal structure composed of carbon atoms, and has excellent optical, electrical, thermal, and mechanical properties. For example, single-layer graphene has a charge transfer rate of up to about 2×105 cm2/Vs, which is faster than the charge transfer rate of silicon by 100 times, and has a current density of about 108 A/cm2, which is greater than the current density of copper by 100 times. As a result, single-layer graphene has a significant potential to be used in fields of nanoscale electronic devices, sensor devices, and photoelectric devices.
At present, main manners for preparing single-layer graphene include mechanical exfoliation method, redox method, and chemical vapor deposition (CVD) method. CVD method is a method of forming graphene by adsorbing hydrocarbon gases such as methane, ethylene and the like on the surface of a catalyst metal substrate at a high temperature and performing decomposition and recombination under the catalysis of the metal. Compared to mechanical exfoliation method and redox method, CVD method is able to prepare single-layer graphene with a large area, and thus attracts extra concerns of scientists.
However, CVD method itself has great defects. Generally, CVD method is carried out in a high-temperature furnace, and the grown graphene is completely attached on catalyst metal after growth is finished. An additional transfer step is further required to practically apply the graphene prepared by this method to devices. Transfer typically needs for soaking in FeCl3 solution for more than ten hours to etch off the catalyst metal substrate and then dredging the graphene using a target substrate and drying it. The whole process is time consuming and labor intensive and is not easily controllable. Furthermore, impurities would be introduced, and even damage of graphene would be caused. These impurities and defects directly affect electrical properties of graphene.
Accordingly, the technical problem to achieve a method capable of directly forming graphene on a target substrate is strongly desirable to be solved by those skilled in the art.